Improvement rates in adolescent patients with chronic fatigue syndrome after receiving cognitive behavioural therapy. Correspondence in response to: Clinical Practice: Chronic fatigue syndrome—Author's reply
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- Nijhof, S.L., Werker, C.L. & van de Putte, E.M. Eur J Pediatr (2014) 173: 693. doi:10.1007/s00431-013-2235-9
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Doctor Courtney questions the definition of recovery in adolescent chronic fatigue syndrome (CFS) in our recent paper . We do agree with Doctor Courtney that defining recovery of (adolescent) CFS is complex; no uniform international agreement exists. The Fatigue in Teenagers on the Internet (FITNET) trial indeed post hoc defined a combined end point, where four criteria had to be met: normalization of school attendance, recovery of fatigue scores and physical functioning to normal ranges, and a self-reported improvement . Normality was defined as being within 2 SD of a healthy peer group [5, 6]. It is important to bear in mind that the peer group in the FITNET study were selected for their good health, as adolescents who suffered from a somatic or psychological illness were excluded . Knoop et al. recently proposed to operationalize recovery criteria as scoring within 1 SD of the healthy (adult) population, but only regarding two criteria (fatigue and physical disability) . In our opinion, school attendance is an important, objective and reliable marker of social and academic participation. Normalization of school attendance, together with self-rated improvement, is therefore essential elements of recovery. International agreements on criteria for the recovery of (adolescent) CFS would greatly improve the comparability of trial outcomes.
Doctor Courtney refers to two correspondences to the FITNET trial [1, 10] that question the definition of recovery. More specifically, it was debated that entry criteria could be virtually the same as recovery criteria. The baseline data of the FITNET trial population showed very severely fatigued and impaired adolescents, not even close to the cut-off points for recovery, as was already stated in the author reply . More importantly, the FITNET study provided analyses at other cut-off points for recovery, namely ±1 SD . While this obviously changed the percentages of recovered patients, the relative effect of FITNET compared to care as usual was unchanged. The main conclusions on web-based cognitive behavioural therapy (CBT) effectiveness thus remained intact: FITNET was superior to usual care at 6 months follow-up.
Doctor Courtney also refers to the long-term follow-up paper (LTFU) of the FITNET trial , in which the long-term outcome of CFS in adolescents was mostly favourable. However, Doctor Courtney's conclusion that receiving CBT did not significantly influence recovery rates is incorrect. Instead, the paper concludes that (1) the short-term effectiveness of web-based CBT is maintained at LTFU and (2) usual care led to similar recovery rates, although these rates were achieved at a slower pace. The scope of this LTFU study was to assess the sustainability of FITNET treatment, rather than to compare FITNET with usual care. After 6 months, the FITNET randomised clinical trial ended and the patients were offered a cross-over possibility. A considerable number of patients under usual care crossed over to FITNET; only a minority received solely usual care. Moreover, almost all adolescents in this group received conventional face-to-face CBT. This difference in pace of recovery underlines once more the importance of accessible, flexible and effective treatment options for this vulnerable age group.
Finally, Doctor Courtney states additional improvement rates of the studies by Stulemeijer et al.  and Knoop et al. . In our article, we obviously refer to the total number of patients who benefit from CBT. To put their results in the context, the study of Stulemeijer et al.  proved that there were significant differences between face-to-face CBT and the waiting list control group: fatigue within normal ranges 60 vs. 21 %, normal physical functioning 63 vs. 24 %, full school attendance 58 vs. 29 % and self-rated improvement 71 vs. 44 %. The long-term follow-up of this study  showed that fatigue severity and physical functioning outcomes were comparable to the assessment immediately post-treatment. The percentage of patients with a full school and/or work attendance for the CBT group was 69 %. These numbers correspond with the 60–70 % improvement and recovery rates as mentioned in our article.